The standard coffee grinder, those inexpensively purchased for about $10-30 US Dollars (USD), uses metal blades in order to grind coffee beans. The blades are centered underneath the beans, and are similar in appearance to the blades of a blender. Theoretically, a really strong blender could do the same work as a coffee grinder, but it would be a much messier process.
An alternative to the standard and less expensive coffee grinder is the burr grinder. This has a very different appearance and functions in a way different from the “blender-like” coffee grinder mentioned above. People may prefer them, because it is easier to regulate the specific kind of coffee you want due to their method of grinding.
The burr grinder uses a moving wheel in addition to blades (in some models). The tension of this sharp wheel grinding away at beans set on a flat surface helps to get the job done, but the speed of the wheel burr grinder often makes the process a little bit messier. Most of these grinders do feature an adjustable wheel, which helps to better regulate grind, and the wheel can be set into different positions (higher or lower) which determine the rough or fine quality of the ground beans. With the cheaper grinders, it’s more guesswork in determining how well your grind will match what you want, and size of the final grind depends on how long you allow the beans to grind.
Burr grinder styles usually have a bottom cup or holding receptacle into which the ground coffee is released, so that as coffee gets to the grind you want, it leaves the grinding area and drops down into this holding area. Burr grinders usually can grind more beans at a time — a standard coffee grinder might hold about 4 ounces (113.4 grams) of beans, but the burr grinder may hold as much as 8 ounces (226.8 grams. Commercial varieties like those you see at grocery stores where you can grind your own coffee will hold even more.
The burrs are essentially rings that fit between or around the coffee blade wheel. Some machines come with two sets, where one burr turns and the other remains stationary. Many prefer conical burr grinders, which tend to be significantly more expensive, because they have cone like edges on the rings that produce a more consistent grind. These also grind more slowly, eliminating any chance of burning the beans through heat produced by the grinder.
This is the main contention among those who favor burr grinders; the burrs helps to reduce the heat of the blades which can burn the coffee and result in inconsistent grind. For coffee aficionados, inconsistent grind means producing a less tasty coffee that may be more bitter in taste. The real coffee fans among us will usually choose a conical over the flat burr grinder type, though the extra expense can be significant.
You can expect to pay anywhere from $30-80 USD for a flat burr grinder. Most conical burr grinders are at least $100 USD, but many cost over $200 USD. You can find these grinders in housewares departments, at stores like Target®, from various Internet vendors, and often in coffee stores.